1. Field of the Invention
The present invention relates to a xenon lamp drive unit used for an artificial solar light irradiation unit which radiates artificial solar light, and a method for driving a xenon lamp.
2. Description of the Related Art
An artificial solar light irradiation unit is known which irradiates an irradiation target with artificial solar light reproducing the spectral distribution of natural solar light for measurement of performances of various apparatuses utilizing solar energy, such as photoelectric conversion characteristics of solar cells. In an artificial solar light irradiation unit of this kind, a light source including a xenon lamp (hereinafter referred to as “lamp”) is set in a box, and light from the light source passes through an optical filter and thereby is radiated as artificial solar light from a radiation surface.
The artificial solar light irradiation unit uses a lamp having an emission length of 1000 mm or more, for example; is supplied with a direct lamp current; and controls the illuminance on an irradiation surface by adjusting the value of the lamp current with a drive unit. In general, the lamp current for driving is about several tens of amperes (for example, 70 A), and the lamp voltage is about several hundreds of volts (for example, 500 V). The lamp current/voltage are supplied/applied for several tens mSec to several hundreds mSec per flash. This output state is controlled by using a constant current or a constant power, and the performances of the irradiation target are measured during the period of the driving. For example, Japanese Patent Application Laid-open No. 2009-283846 discloses an artificial solar light irradiation unit in which the lamp current is controlled by using a constant current.
In the above case, the lamp power is 35 kW, which causes the following problems. Specifically, when the power is supplied directly from mains electricity supply even for an instant (for example, 100 mSec), peripheral devices on the same line of the mains electricity supply are adversely affected. Moreover, a large-capacity contact and a large-capacity wiring are necessary between the mains electricity supply and an irradiation unit. For these reasons, a configuration is employed in general in which a drive unit is provided in the irradiation unit, and the drive unit stores power, and supplies the stored power to a lamp in response to an operation instruction.